English Translation
The camera caught the man stealing in the store.
Why is Stehlen capitalized?
Welcome to the forums @OttoOttoOtto 
I think this is a case of a “substantiviertes Verb”. You can turn verbs into nouns. They are then capitalized like regular nouns.
stehlen → das Stehlen (not 100% sure about the article, but ‘der’ and ‘die’ sound off to me)
Thanks HerrSubset, that makes sense.
Time for me to learn more about substantivertes Verben and Das Gerund.
Harder to learn a new language when one’s grammer in general is weak.
You’ll get there step by step 
Also, there’s some native German speakers in the forums here (not me) that can explain things very well. So don’t be afraid to ask!